1. Field of the Invention
This invention relates to a liquid-filled elastomeric bushing for use in automobiles, industrial machines and the like developing an effective damping action.
2. Description of the Prior Art
Heretofore, there have been known liquid-filled elastomeric bushings, wherein the damping of vibrations is mainly performed by a flow resistance subjected to an incompressible liquid enclosed in liquid chambers. Such is disclosed, for example, in German Patent Specification No. 2,841,505.
Such an elastomeric bushing comprises an inner sleeve, an outer sleeve, an elastomeric member interposed between the inner and outer sleeves and provided with recesses constituting liquid chambers, and an intermediate sleeve disposed between the outer periphery of the elastomeric member and the outer sleeve and provided with holes corresponding to the contour profile of the liquid chamber and with restricted passages formed in the outer periphery thereof to establish communication between the liquid chambers.
In this liquid-filled elastomeric bushing, however, the fixing of the outer sleeve to the intermediate sleeve is generally carried out by squeezing, so that there is a fear that the restricted passage formed in the outer periphery of the intermediate sleeve of rigid material is deformed by the squeezing to deteriorate the given damping action. Furthermore, the deformations in circumferential and axial directions of the elastomeric member are caused by the incompressible liquid in the liquid chamber during squeezing, while the intermediate sleeve fixed to the outer periphery of the elastomeric member acts to restrain these deformations, so that a large initial stress is locally applied to the interior of the elastomeric member and the joint surface between the elastomeric member and the intermediate sleeve. That reduces the durability of the elastomeric bushing and produces the vibration damping performance.
Moreover, since the intermediate sleeve is constituted by forming plural holes in the hollow cylindrical member having a length substantially equal to the elastomeric bushing, the number of the working steps and material cost of the intermediate sleeve become higher and also the weight of the elastomeric bushing becomes undesirably large.